From my experience, as a cyclist speed and acceleration helps with avoiding car-related danger. If you're fast enough, cars won't needlessly overtake you (in rush hour, most car traffic may not exeed 30 km/h for example due to roads being packed too full, that's easy to match for a trained cyclist).
Also at intersections, being really quick at acceleration allows you to get out of the danger zone of cars crossing your path before there's a conflict. Think about right-turning trucks starting after a red traffic light.
I think fitness (and maybe reaction time) is some reason why severe cycling accidents seem to happen to older cyclist at a higher rate. In Berlin out of 15 cycling deaths this year, more than half of them are age 60 and higher [1], 3 are beyond 80 years of age.
[1] https://adfc-berlin.de/radverkehr/sicherheit/information-und...